Why is combustion exothermic and what role does oxygen's electronegativity play?

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    Combustion Exothermic
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Discussion Overview

The discussion centers around the atomic mechanism of combustion, specifically why it is exothermic and the role of oxygen's electronegativity in its reactivity with hydrocarbons. The scope includes theoretical aspects of chemistry and the energy dynamics involved in combustion reactions.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • One participant inquires about the atomic mechanism that makes combustion exothermic and the reactivity of O2 with hydrocarbons.
  • Another participant suggests that the depth of the answer can vary based on the level of detail desired.
  • A participant with first-year university chemistry knowledge expresses interest in a detailed explanation, noting difficulty in finding information online.
  • One explanation posits that combustion involves the rearrangement of atoms into new combinations, and whether a process is exothermic or endothermic depends on the energy states of the reactants and products.
  • It is mentioned that CO2 is at a lower energy state compared to O2 and hydrocarbons, leading to the release of heat during combustion.
  • Another point raised is that oxygen's high electronegativity allows it to "steal" bonds from carbon, with a reference to the stability of full electron shells in the periodic table.

Areas of Agreement / Disagreement

Participants have not reached a consensus on the specifics of the atomic mechanisms involved in combustion or the implications of oxygen's electronegativity, indicating that multiple viewpoints and uncertainties remain in the discussion.

Contextual Notes

There are limitations in the discussion regarding the assumptions about energy states and the definitions of exothermic and endothermic processes, which have not been fully explored or resolved.

fysik
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hello!

what is the atomic mechanism of combustion that makes it so exothermic?

what makes O2 so reactive with hydrocarbons for example and why is the reaction exothermic?

thanks
 
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Do you know anything about chemistry? The answer can be fairly in depth depending on what level of detail you want to get into.
 
yes, I know first years uni chemistry
yes, I am looking for the deepest I can get, or a little less, that's ok
at least something, because I can't find something online at all!
I think it has to do with oxygen roots that are highly reactive
but why are they so reactive?
 
In the end it's all a question of energy. During combustion, the molecules' atoms of two substances get rearranged into new combinations. Whether a process is exothermic or endothermic depends on whether the final product is energetically lower or not. CO2 is energetically a lower state than O2 or hydrocarbons respectively. So, once you overcome the energy that keeps the O2 molecules together (and the hydrocarbons too), they can recombine into CO2 for example. Because the final energy state is lower, the energy difference ends up as heat. Which means, the reaction is exothermic.
 
Oxygen has a high electronegativity so it likes to steal away the bonds from carbon. The highest electronegativities are on the top right of the periodic table to the left of the noble gases. That's because a full shell is very stable. Any additional electrons over a full shell have to go to a higher energy shell, which means these electrons take less energy to release.
 

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